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[2] HS2 vs [1] HS4

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Atrus

Atrus

Jedi Warrior
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Once again, per my Megasquirt post on this page, I am trying to determine what I'd want to use as a throttle plate for an FI setup.

I may be thinking about this all wrong, however, currently my 1275 has 2 HS2's. For ease of implementing an FI system, I was now considering swapping to a single HS4.

HS4 = 1.50" = 1.767 sq. inches
HS2 = 1.25" = 1.227 sq inches, multipled by 2 = 2.454

So, wouldn't a HS4 be restrictive on the engine?

P.S. - I am awaiting Vizard's book to arrive, so bear with me! /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
 
Kevin, most of the 1275 single carb conversions I've seen use a single HIF 44. Roughly a 1.732" throttle bore.
I ran a single HS4 on my 1500 Spit, but it was heavily tweaked for racing.
Jeff
 
Jeff,

Like I said, no Vizard's book yet, but basically I want to perk the engine up a little - maybe some mild head work (porting/polishing), street cam, perhaps a bore - .020" or .030". It's all speculation now until I really read up on how these engines respond to various mods, however, I'd just like to make the car a little quicker and peppier for cruising around here on weekends.

So, if most people do the HIF 44, I'd be safe to think the HS4 isn't being too restrictive?
 
Kevin, depending on the attendant mods, I think you can get away with a single HS4. The HIF 44 is a metric carb, ie 44mm bore, or nearly 1 3/4".
But, on a high performance 1275 I run twin HS4's. The only reason I ran a single on the 1500 was due to rules restrictions.
Jeff
 
if you could find a HIF 44 you would either have to build your own manifold or get one off of a mg metro and the single is what i am thinking of doing on my 948cc just because i don't want to have to tune two carbs
 
A single HIF 44 is <u>way</u> too much carb for a 948. Remember, they had 1 1/8" carbs originally.
But, what do I know?
Jeff
 
upon further research i am going to do a single 1.5...and i have an mk2 which means that i have a 9cc enging which means 1 1/4 inch carbs
 
Bugeye58 said:
But, what do I know?
Click to expand...
Jeff...you've probably forgot more than most of us will know about these little cars. Keep the advice coming.
JC
 
Would you say a 56mm bore on the throttle would be far too big for a lightly modded 1275? (I'm scheming)
 
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